Ethylene copolymers containing carboxyl groups, such as those described in U.S. Pat. No. 3,520,861, are well known. However, ethylene copolymers containing pendant carboxyl groups are inherently susceptible to thermal instability. In the production of such ethylene copolymers, this inherent instability poses a significant problem because of crosslinking of the polymer, variation in melt flow values, and the formation of crosslinking by-products which are corrosive to process equipment. In addition, the instability seriously limits the useful life of products made from these ethylene copolymers, including films, coatings, adhesives, and the like.
Thermal stabilizing additives heretofore employed in conjunction with carboxyl-containing ethylene copolymers have not provided satisfactory results. Likewise, the injection of steam into molten ethylene copolymers containing carboxyl groups has not provided satisfactory results and, in addition, has the further disadvantages of adversely affecting the quality of products made from the copolymers and corroding processing equipment.